A high-pressure discharge lamp with discharge vessel is known from U.S. Pat. Nos. 6,198,223 and 6,268,698 in which an ignition aid is executed as a winding around one end of the discharge vessel.
Radioactivity-free lamps require significantly higher ignition pulses than lamps with radioactive substances in the discharge vessel. In the case of general lighting, however, often only an ignition pulse of 4-5 kV is available on account of the ignitors used. Therefore ignition aids are often used to reduce the ignition voltage of the lamp by means of auxiliary structures. Various embodiments of such ignition aids are known, in which the electrical potential of one electrode is brought into proximity with the counter electrode with the aid of electrically conducting components outside the discharge vessel. To this end as a rule a wire, clip or the like is wound around the fusing, pinch or capillary tube in the proximity of the electrode and electrically connected to the current supply of the counter electrode. When the ignition voltage is applied in the region of the enclosed electrode a dielectric barrier discharge is thus produced inside the discharge vessel, which ionizes the burner filler gas and reduces the ignition voltage, see EP967631.
In the case of lamps whose discharge vessel is made of quartz glass or certain types of ceramics and contains sodium as a filling component, however, ignition aids assembled in this way result in sodium escape if they are electrically connected to one of the two current supplies. The phenomenon of sodium escape is known per se. For the lamp the loss of sodium from the discharge vessel signifies a significant impairment of the quality of light as the color temperature clearly alters and it may even go out.
In order to avoid sodium escape, it is possible to connect the ignition aid arrangement only capacitively to the electrodes, as described in WO2008154102A2, for example. However, a major disadvantage of capacitively connected ignition aids is that they are significantly less effective compared with directly contacted electric ignition aids, so that in the case of ignition pulses in the range of 4-5 kV it is often not possible to initiate discharge.